Bi-Component Fibers and Nonwoven Materials Produced Therefrom

ABSTRACT

A method can include (a) extruding a bi-component fiber comprising: a first component comprising a first polypropylene homopolymer; and a second component comprising a blend that comprises a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater than or at least 20% less than a melt flow rate of the first polypropylene homopolymer; (b) cooling the bi-component fiber; and (c) thermally and/or mechanically activating the bi-component fiber to cause the bi-component fiber to curl.

PRIORITY

This application claims priority to and the benefit of U.S. ProvisionalApplication No. 62/732,599, filed Sep. 18, 2018, and European PatentApplication No. 18199603.4, which was filed Oct. 10, 2018, thedisclosures of which are incorporated herein by reference in theirentireties.

FIELD

The present disclosure relates to bi-component fibers that when used toproduce nonwoven materials enhance the loft of the nonwoven material.

BACKGROUND

Synthetic fibers and nonwoven fabrics often lack a soft feel or “hand”like natural fibers and fabrics. The different aesthetic feeling is dueto the lack of “loft” or “bulk” in synthetic materials versus the innatespace-filling characteristics of natural fibers. Natural fibers areoften not planar materials, and rather they exhibit some crimp ortexture in three-dimensions that allow for space between fibers. Naturalfibers can often be laid onto a plane and have a surface projecting fromthat plane, which are “3-dimensional.” By contrast, synthetic fibers areessentially planar. There are a number of methods to impart “bulkiness”or “loft” to synthetic fibers or fabrics, including mechanicaltreatments such as crimping, air jet texturing, or pleating. Thesemethods are not generally easily applicable to spunbond nonwoven fabricsin cost-effective ways.

SUMMARY

A first embodiment is a method comprising (or consists of, or consistsessentially of): (a) extruding a bi-component fiber comprising: a firstcomponent comprising a first polypropylene homopolymer; and a secondcomponent comprising a blend that comprises a propylene-based elastomerand a second polypropylene homopolymer, wherein the blend has a meltflow rate that is at least 20% greater than or at least 20% less than amelt flow rate of the first polypropylene homopolymer; (b) cooling thebi-component fiber; and (c) thermally and/or mechanically activating thebi-component fiber to cause the bi-component fiber to curl.

A second embodiment is a bi-component fiber comprising: a firstcomponent comprising a first polypropylene homopolymer; and a secondcomponent comprising a blend that comprises a propylene-based elastomerand a second polypropylene homopolymer, wherein the blend has a meltflow rate that is at least 20% greater than or at least 20% less than amelt flow rate of the first polypropylene homopolymer.

A third embodiment is a nonwoven article comprising the bi-componentfiber of the second embodiment.

A fourth embodiment is a laminated article comprising the bi-componentfiber of the second embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of theembodiments, and should not be viewed as exclusive embodiments. Thesubject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to those skilled in the art and having the benefit of thisdisclosure.

FIG. 1 is a plot of the shrinkage (ASTM D2259-02(2016)) of examplefibers.

FIG. 2A is a scanning electron micrograph of as-produced bi-componentfibers before mechanical activation.

FIG. 2B is a scanning electron micrograph of as-produced bi-componentfibers after mechanical activation.

FIGS. 3A and 3B are light micrographs of the fibers as-produced beforethermal activation.

FIGS. 3C and 3D is that sample after thermal activation at 100° C. for15 seconds.

FIG. 4 is a plot of the shrinkage (ASTM D2259-02(2016)) of examplefibers.

DETAILED DESCRIPTION

The present disclosure relates to bi-component fibers that when used toproduce nonwoven materials enhance the loft of the nonwoven material.More specifically, the bi-component fibers comprise a first componentcomprising a first polypropylene homopolymer and a second componentcomprising a blend that comprises a propylene-based elastomer and asecond polypropylene homopolymer. The blend has a melt flow rate that isat least 20% greater or at least 20% less than a melt flow rate of thefirst polypropylene homopolymer. That is, if the melt flow rate of thefirst polypropylene homopolymer is 36 g/10 min (ASTM D1238-13, 2.16 kg,230° C.), then the melt flow rate of the blend is greater than 43 g/10min (ASTM D1238-13, 2.16 kg, 230° C.) or less than 29 g/10 min (ASTMD1238-13, 2.16 kg, 230° C.).

Definitions

As used herein, “extrude” or “extruded” or “extruding” means that amaterial in its molten or flowable state is forced through a mechanicalcontainment means such as a tube, pre-formed mold, die (preferably of adesired narrowing diameter and/or shape), or extruder, heated orotherwise, such that the material flows from a one point to another,such as a source of unmelted polymer to form a molten stream of suchpolymer in a stream or formed stream.

As used herein, “spunbond” refers to a meltspinning method of forming afabric in which a polymeric melt or solution is extruded throughspinnerets to form filaments which are cooled then attenuated bysuitable means such as by electrostatic charge or high velocity air,such attenuated filaments (“fibers”) then laid down on a moving screento form the fabric. Fibers resulting from a spunbond process typicallyhave some degree of molecular orientation imparted therein.

As used herein, “meltblown” refers to a method of forming a fabric inwhich a polymeric melt or solution is extruded through spinnerets toform filaments which are attenuated by suitable means such as byelectrostatic charge or high velocity air, such attenuated filaments(“fibers”) are then laid down on a moving screen to form the fabric. Thefibers themselves may be referred to as being “spunbond” or “meltblown.”

As used herein, the term “coform” refers to another meltspinning processin which at least one meltspun die head is arranged near a chute throughwhich other materials are added to the fabric while it is forming. Suchother materials may be pulp, superabsorbent particles, cellulose orstaple fibers, for example. Coform processes are described in U.S. Pat.Nos. 4,818,464 and 4,100,324. For purposes of this disclosure, thecoform process is considered a particular embodiment of meltspunprocesses. In certain embodiments, the propylene-based fabrics describedherein are coform fabrics.

As used herein, a “fiber” is a structure whose length is very muchgreater than its diameter or breadth; the average diameter is on theorder of 0.1 μm to 250 μm, and comprises natural and/or syntheticmaterials. Fibers can be “monocomponent” or “bi-component.” Bi-componentfibers comprise two of different chemical and/or physical propertiesextruded from separate extruders but the same spinnerets with bothpolymers within the same filament, resulting in fibers having distinctdomains. The configuration of such a bi-component fiber may be, forexample, sheath/core arrangement wherein one polymer is surrounded byanother, side-by-side as described in U.S. Pat. No. 5,108,820, orislands in the sea as described in U.S. Pat. No. 7,413,803.

Any “web” of fibers, regardless of how formed, may be used as it is(unbonded) or bonded such as by heating, for example, by passing the webof fibers over a heated calender or roll.

As used herein, a “laminate” comprises at least two fabrics and/or filmlayers. Laminates may be formed by any means known in the art. Such alaminate may be made, for example, by sequentially depositing onto amoving forming belt first a meltspun fabric layer, then depositinganother meltspun fabric layer or adding a dry-laid fabric on top of thefirst meltspun fabric layer, then adding a meltspun fabric layer on topof those layers, followed by some bonding of the laminate, such as bythermal point bonding or the inherent tendency of the layers to adhereto one another, hydroentangling, and the like. Alternatively, the fabriclayers may be made individually, collected in rolls, and combined in aseparate bonding step or steps. Multilayer laminates may also havevarious numbers of layers in many different configurations and mayinclude other materials like films or coform materials, meltblown andspunbond materials, air-laid materials, and the like.

As used herein, a “film” is a flat unsupported section of a plasticand/or elastomeric material whose thickness is very narrow in relationto its width and length and has a continuous or nearly continuousmacroscopic morphology throughout its structure allowing for the passageof air at diffusion-limited rates or lower. The laminates describedherein may include one or more film layers and can comprise any materialas described herein for the fabrics. In certain embodiments, films areabsent from the laminates described herein. Films described herein maycontain additives that, upon treatment, promote perforations and allowthe passage of air and/or fluids through the film. Additives such asclays, antioxidants, and the like as described herein can also be added.

Polypropylene Homopolymer

The bi-component fibers of the present invention comprise a firstcomponent comprising a first polypropylene homopolymer and a secondcomponent comprising a blend that comprises a propylene-based elastomerand a second polypropylene homopolymer. The first and secondpolypropylene homopolymers can be the same or different. As used herein,the term “propylene homopolymer” refers to polymers with only propylenemonomer units and is used to generally describe the first and secondpropylene homopolymers. That is, the propylene homopolymer compositionsand properties are suitable for the first propylene homopolymer and/orthe second propylene homopolymer.

In certain embodiments, the polypropylene homopolymer is predominatelycrystalline, as evidenced by having a melting point generally greaterthan 110° C., alternatively greater than 115° C., and most preferablygreater than 130° C., or within a range from 110° C., or 115° C., or130° C. to 150° C., or 160° C., or 170° C. The term “crystalline,” asused herein, characterizes those polymers which possess high degrees ofinter- and intra-molecular order. The polypropylene preferably has aheat of fusion greater than 60 J/g, alternatively at least 70 J/g,alternatively at least 80 J/g, as determined by DSC analysis. The heatof fusion is dependent on the composition of the polypropylene.

The weight average molecular weight (Mw) of the polypropylenehomopolymer can be within a range from 40,000 g/mole or 50,000 g/mole,or 80,000 g/mole to 200,000 g/mole, or 400,000 g/mole, or 500,000g/mole, or 1,000,000 g/mole. The number average molecular weight (Mn) iswithin a range from 20,000 g/mole, or 30,000 g/mole, or 40,000 g/mole to50,000 g/mole, or 55,000 g/mole, or 60,000 g/mole, or 70,000 g/mole. Thez-average molecular weight (Mz) is at least 300,000 g/mole, or 350,000g/mole, or within a range from 300,000, or 350,000 g/mole to 500,000g/mole. The molecular weight distribution, Mw/Mn, in any embodiment isless than 5.5, or 5, or 4.5, or 4, or within a range from 1.5, or 2, or2.5, or 3 to 4, or 4.5 or 5 or 5.5.

The melt flow rate (MFR) of the polypropylene homopolymer can be withina range from 1 g/10 min to 500 g/10 min, alternatively within a rangefrom 1 g/10 min, or 5 g/10 min, or 10 g/10 min, or 15 g/10 min, or 20g/10 min, or 25 g/10 min to 45 g/10 min, or 55 g/10 min, or 100 g/10min, or 300 g/10 min, or 350 g/10 min, or 400 g/10 min, or 450 g/10 min,or 500 g/10 min, as measured per ASTM D1238-13 with a 2.16 kg load at230° C. (ASTM D1238-13, 2.16 kg, 230° C.).

There is no particular limitation on the method for preparing thepolypropylene homopolymer of the invention. For example, the polymer maybe a propylene homopolymer obtained by homopolymerization of propylenein a single stage or multiple stage reactor. Polymerization methodsinclude high pressure, slurry, gas, bulk, or solution phase, or acombination thereof, using a traditional Ziegler-Natta catalyst or asingle-site, metallocene catalyst system, or combinations thereofincluding bimetallic supported catalyst systems. Polymerization may becarried out by a continuous or batch process and may include use ofchain transfer agents, scavengers, or other such additives as deemedapplicable. Most preferably however a Ziegler-Natta catalyst is used toform the polypropylene homopolymer.

The polypropylene homopolymer may be reactor grade, meaning that it hasnot undergone any post-reactor modification by reaction with peroxides,cross-linking agents, e-beam, gamma-radiation, or other types ofcontrolled rheology modification. In any embodiment, the polypropylenehomopolymer may have been visbroken by peroxides as is known in the art.In any case, the polyolefins used in the examples set forth here, anddescribed above, have the stated properties as used, visbroken or not.

Exemplary commercial products of the polypropylene polymers inpolypropylene homopolymer ExxonMobil™ PP3155 (a 36 g/10 min MFR (ASTMD1238-13, 2.16 kg, 230° C.) homopolymer, available from ExxonMobilChemical Company), ExxonMobil™ PP3155E5 (a 36 g/10 min MFR (ASTMD1238-13, 2.16 kg, 230° C.) homopolymer, available from ExxonMobilChemical Company), ExxonMobil™ PP1264E1 (a 20 g/10 min MFR (ASTMD1238-13, 2.16 kg, 230° C.) homopolymer, available from ExxonMobilChemical Company), ExxonMobil™ PP1105E1 (a 35 g/10 min MFR (ASTMD1238-13, 2.16 kg, 230° C.) homopolymer, available from ExxonMobilChemical Company), ExxonMobil™ PP1074KNE1 (a 20 g/10 min MFR (ASTMD1238-13, 2.16 kg, 230° C.) homopolymer, available from ExxonMobilChemical Company), Achieve™ Advanced PP1605 (a 32 g/10 min MFR (ASTMD1238-13, 2.16 kg, 230° C.) homopolymer, available from ExxonMobilChemical Company), and Achieve™ Advanced PP3854 (a 24 g/10 min MFR (ASTMD1238-13, 2.16 kg, 230° C.) homopolymer, available from ExxonMobilChemical Company).

The bi-component fibers comprise a first component comprising a firstpolypropylene homopolymer and a second component comprising a blend thatcomprises a propylene-based elastomer and a second polypropylenehomopolymer.

The amount of polypropylene homopolymer or blend of propylenehomopolymers in the first component can be 80 wt % to 100 wt % based onthe weight of the first component, or 90 wt % to 99 wt %, or 95 wt % to98 wt %. The first component can optionally further comprise additivesdescribed herein.

The amount of polypropylene homopolymer or blend of propylenehomopolymers in the second component can be 10 wt % to 90 wt % based onthe weight of the second component, or 20 wt % to 50 wt %, or 50 wt % to80 wt %. The second component can optionally further comprise additivesdescribed herein.

Propylene-Based Elastomer

The propylene-based elastomer as described herein is a copolymer ofpropylene-derived units and units derived from at least one of ethyleneor a C₄ to C₁₀ α-olefin. The propylene-based elastomer may contain atleast 50 wt % propylene-derived units. The propylene-based elastomer mayhave limited crystallinity due to adjacent isotactic propylene units anda melting point as described herein. The crystallinity and the meltingpoint of the propylene-based elastomer can be reduced compared to highlyisotactic polypropylene by the introduction of errors in the insertionof propylene. The propylene-based elastomer is generally devoid of anysubstantial intermolecular heterogeneity in tacticity and comonomercomposition, and also generally devoid of any substantial heterogeneityin intramolecular composition distribution.

The amount of propylene-derived units present in the propylene-basedelastomer may range from an upper limit of 95 wt %, 94 wt %, 92 wt %, 90wt %, or 85 wt %, to a lower limit of 60 wt %, 65 wt %, 70 wt %, 75 wt%, 80 wt %, 84 wt %, or 85 wt % of the propylene-based elastomer. Thecomonomer-derived units include at least one of ethylene or a C₄ to C₁₀α-olefin may be present in an amount of 1 wt % to 35 wt %, or 5 wt % to35 wt %, or 7 wt % to 32 wt %, or 8 wt % to 25 wt %, or 8 wt % to 20 wt%, or 8 wt % to 18 wt %, of the propylene-based elastomer. The comonomercontent may be adjusted so that the propylene-based elastomer has a heatof fusion of less than 80 J/g, a melting point of 105° C. or less, and acrystallinity of 2% to 65% of the crystallinity of isotacticpolypropylene, and a MFR within a range from 2 g/10 min to 50 g/min(ASTM D1238-13, 2.16 kg, 230° C.).

In preferred embodiments, the comonomer is ethylene, 1-hexene, or1-octene, with ethylene being most preferred. In embodiments where thepropylene-based elastomer comprises ethylene-derived units, thepropylene-based elastomer may comprise 5 wt % to 25 wt %, or 8 wt % to20 wt %, or 9 wt % to 16 wt %, ethylene-derived units. In someembodiments, the propylene-based elastomer consists essentially of unitsderived from propylene and ethylene, that is, the propylene-basedelastomer does not contain any other comonomer in an amount other thanthat typically present as impurities in the ethylene and/or propylenefeedstreams used during polymerization, or in an amount that wouldmaterially affect the heat of fusion, melting point, crystallinity, ormelt flow rate of the propylene-based elastomer, or in an amount suchthat any other comonomer is intentionally added to the polymerizationprocess.

In some embodiments, the propylene-based elastomer may comprise morethan one comonomer. Preferred embodiments of a propylene-based elastomerhaving more than one comonomer include propylene-ethylene-octene,propylene-ethylene-hexene, and propylene-ethylene-butene polymers. Inembodiments where more than one comonomer derived from at least one ofethylene or a C₄ to C₁₀ α-olefin is present, the amount of one comonomermay be less than 5 wt % of the propylene-based elastomer, but thecombined amount of comonomers of the propylene-based elastomer is 5 wt %or greater.

The propylene-based elastomer may have a triad tacticity of threepropylene units, as measured by ¹³C NMR, of at least 75%, at least 80%,at least 82%, at least 85%, or at least 90%. Preferably, thepropylene-based elastomer has a triad tacticity of 50% to 99%, or 60% to99%, or 75% to 99%, or 80% to 99%. In some embodiments, thepropylene-based elastomer may have a triad tacticity of 60% to 97%.

The propylene-based elastomer has a heat of fusion (“H_(f)”), asdetermined by DSC, of 80 J/g or less, or 70 J/g or less, or 50 J/g orless, or 40 J/g or less. The propylene-based elastomer may have a lowerlimit H_(f) of 0.5 J/g, or 1 J/g, or 5 J/g. For example, the H_(f) valuemay range from 1.0 J/g, 1.5 J/g, 3.0 J/g, 4.0 J/g, 6.0 J/g, or 7.0 J/g,to 30 J/g, 35 J/g, 40 J/g, 50 J/g, 60 J/g, 70 J/g, 75 J/g, or 80 J/g.

The propylene-based elastomer may have a percent crystallinity, asdetermined according to the DSC procedure described herein, of 2% to65%, or 0.5% to 40%, or 1% to 30%, or 5% to 35%, of the crystallinity ofisotactic polypropylene. The thermal energy for the propylene of 100%crystallinity is estimated at 189 J/g. In some embodiments, thecopolymer has crystallinity less than 40%, or within a range from 0.25%to 25%, or within a range from 0.5% to 22% of the crystallinity ofisotactic polypropylene.

In some embodiments, the propylene-based elastomer may further comprisediene-derived units (as used herein, “diene”). The optional diene may beany hydrocarbon structure having at least two unsaturated bonds whereinat least one of the unsaturated bonds is readily incorporated into apolymer. For example, the optional diene may be selected from straightchain acyclic olefins, such as 1,4-hexadiene and 1,6-octadiene; branchedchain acyclic olefins, such as 5-methyl-1,4-hexadiene,3,7-dimethyl-1,6-octadiene, and 3,7-dimethyl-1,7-octadiene; single ringalicyclic olefins, such as 1,4-cyclohexadiene, 1,5-cyclooctadiene, and1,7-cyclododecadiene; multi-ring alicyclic fused and bridged ringolefins, such as tetrahydroindene, norbornadiene,methyl-tetrahydroindene, dicyclopentadiene,bicyclo-(2.2.1)-hepta-2,5-diene, norbornadiene, alkenyl norbornenes,alkylidene norbornenes, for example, ethylidiene norbornene (“ENB”),cycloalkenyl norbornenes, and cycloalkyliene norbornenes (such as5-methylene-2-norbornene, 5-ethylidene-2-norbornene,5-propenyl-2-norbornene, 5-isopropylene-2-norbornene,5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene,5-vinyl-2-norbornene); and cycloalkenyl-substituted alkenes, such asvinyl cyclohexene, allyl cyclohexene, vinyl cyclooctene, 4-vinylcyclohexene, allyl cyclodecene, vinyl cyclododecene, andtetracyclo-(A-11,12)-5,8-dodecene. The amount of diene-derived unitspresent in the propylene-based elastomer may range from an upper limitof 15%, 10%, 7%, 5%, 4.5%, 3%, 2.5%, or 1.5%, to a lower limit of 0%,0.1%, 0.2%, 0.3%, 0.5%, 1%, 3%, or 5%, based on the weight of thepropylene-based elastomer.

The propylene-based elastomer may have a single peak melting transitionas determined by DSC. In some embodiments, the copolymer has a primarypeak transition of 90° C. or less, with a broad end-of-melt transitionof 110° C. or greater. The peak “melting point” (“T_(m)”) is defined asthe temperature of the greatest heat absorption in melting of thesample. However, the copolymer may show secondary melting peaks adjacentto the principal peak, and/or at the end-of-melt transition. For thepurposes of this disclosure, such secondary melting peaks are consideredtogether as a single melting point, with the highest of these peaksbeing considered the T_(m) of the propylene-based elastomer. Thepropylene-based elastomer may have a T_(m) of 110° C. or less, 105° C.or less, 100° C. or less, 90° C. or less, 80° C. or less, or 70° C. orless. In some embodiments, the propylene-based elastomer has a T_(m) of25° C. to 105° C., or 60° C. to 105° C., or 70° C. to 105° C., or 90° C.to 105° C.

The propylene-based elastomer may have a density of 0.850 g/cm³ to 0.900g/cm³, or 0.860 g/cm³ to 0.880 g/cm³, at 22° C. as measured per ASTMD1505-18.

The propylene-based elastomer may have a melt flow rate (“MFR”), asmeasured per ASTM D1238-13, 2.16 kg at 230° C., of at least 2 g/10 min.In some embodiments, the propylene-based elastomer may have an MFR of 2g/10 min to 50 g/10 min, or 2 g/10 min to 20 g/10 min, or 30 g/10 min to50 g/10 min, or 40 g/10 min to 50 g/10 min.

The propylene-based elastomer may have an elongation at break of lessthan 2000%, less than 1800%, less than 1500%, less than 1000%, or lessthan 800%, as measured per ASTM D412-16.

The propylene-based elastomer may have a weight average molecular weight(Mw) of 5,000 g/mole to 5,000,000 g/mole, or 10,000 g/mole to 1,000,000g/mole, or 50,000 g/mole to 400,000 g/mole. The propylene-basedelastomer may have a number average molecular weight (Mn) of 2,500g/mole to 250,000 g/mole, or 10,000 g/mole to 250,000 g/mole, or 25,000g/mole to 250,000 g/mole. The propylene-based elastomer may have az-average molecular weight (Mz) of 10,000 g/mole to 7,000,000 g/mole, or80,000 g/mole to 700,000 g/mole, or 100,000 g/mole to 500,000 g/mole.Finally, the propylene-based elastomer may have a molecular weightdistribution MWD of 1.5 to 20, or 1.5 to 15, or 1.5 to 5, or 1.8 to 3,or 1.8 to 2.5.

The first component and/or second component of the bi-component fibersdisclosed herein may include one or more different propylene-basedelastomers, such as distinct propylene-based elastomers each having oneor more different properties such as, for example, different comonomeror comonomer content. Such combinations of various propylene-basedelastomers are all within the scope of the invention.

The propylene-based elastomer may comprise copolymers prepared accordingto the procedures described in WO/2002/036651, U.S. Pat. No. 6,992,158,and/or WO/2000/001745. Preferred methods for producing thepropylene-based elastomer may be found in U.S. Pat. Nos. 7,232,871 and6,881,800. The invention is not limited by any particular polymerizationmethod for preparing the propylene-based elastomer, and thepolymerization processes are not limited by any particular type ofreaction vessel.

Suitable propylene-based elastomers may be available commercially underthe trade names Vistamaxx™ (available from ExxonMobil Chemical Company),VERSIFY™ (available from The Dow Chemical Company), certain grades ofTAFMER™ XM or NOTIO™ (available from Mitsui Company), and certain gradesof SOFTEL™ (available from Basell Polyolefins). The particular grade(s)of commercially available propylene-based elastomer suitable for use inthe invention can be readily determined using methods commonly known inthe art.

The amount of propylene-based elastomer or blend of propylene-basedelastomers in the second component can be 10 wt % to 90 wt % based onthe weight of the second component, or 20 wt % to 50 wt %, or 50 wt % to80 wt %. The second component can optionally further comprise additivesdescribed herein.

Blend of the Second Component

The second component of the bi-component fiber comprises a blend thatcomprises a propylene-based elastomer and a second polypropylenehomopolymer.

The blend may have a MFR (ASTM D1238-13, 2.16 kg, 230° C.) of at least 2g/10 min. In some embodiments, the propylene-based elastomer may have anMFR of 2 g/10 min to 50 g/10 min, or 2 g/10 min to 20 g/10 min, or 30g/10 min to 50 g/10 min, or 40 g/10 min to 50 g/10 min. The blend has amelt flow rate that is at least 20% greater or at least 20% less than amelt flow rate of the first polypropylene homopolymer.

The weight ratio of propylene homopolymer(s) to propylene-basedelastomer(s) in the second component can be 10:90 to 90:10, or 20:80 to80:20, or 15:85 to 50:50, or 30:70 to 40:60, or 50:50 to 85:15, or 60:40to 70:30.

Additives

A variety of additives may be incorporated into the propylenehomopolymer and/or blend of the second component described above used tomake the fibers and fabric. Such additives include, for example,stabilizers, antioxidants, fillers, colorants, nucleating agents, andslip additives. Primary and secondary antioxidants include, for example,hindered phenols, hindered amines, and phosphates. Nucleating agentsinclude, for example, sodium benzoate and talc. Also, other nucleatingagents may also be employed such as Ziegler-Natta olefin product orother highly crystalline polymer. Other additives such as dispersingagents, for example, ACROWAX™ C (available from Lonza), can also beincluded. Slip agents include, for example, oleamide and erucamide.Catalyst deactivators are also commonly used, for example, calciumstearate, hydrotalcite, and calcium oxide, and/or other acidneutralizers known in the art.

Other additives include, for example, fire/flame retardants,plasticizers, vulcanizing or curative agents, vulcanizing or curativeaccelerators, cure retarders, processing aids, tackifying resins, andthe like. The aforementioned additives of may also include fillersand/or reinforcing materials, either added independently or incorporatedinto an additive. Examples include carbon black, clay, talc, calciumcarbonate, mica, silica, silicate, combinations thereof, and the like.Other additives which may be employed to enhance properties includeantiblocking agents, lubricants, and nucleating agents. The listsdescribed herein are not intended to be inclusive of all types ofadditives which may be employed with the present invention. Upon readingthis disclosure, those of skill in the art will appreciate otheradditives may be employed to enhance properties. As is understood bythose skilled in the art, the blends of the present invention may bemodified to adjust the characteristics of the blends as desired.

In any embodiment, the blend of the second component described hereincan comprise (or consist of) the propylene-based elastomer, the secondpolypropylene homopolymer, and within a range from 0.1 wt % to 3 wt %,or 4 wt %, or 5 wt % of additives by weight of the blend. Mostpreferably, those additives include primary and secondary antioxidants,acid scavenger, nucleating agent, and pigment or other colorant.

Blending

The blend of the second component described herein may be prepared byany procedure that produces a mixture of the components, for example,dry blending, melt blending, and the like. In certain embodiments, acomplete mixture of the polymeric components is indicated by theuniformity of the morphology of the dispersion of the polymercomponents.

Melt blend: Continuous melt mixing equipment are generally used. Theseprocesses are well known in the art and include single and twin screwcompounding extruders as well as other machines and processes, designedto homogenize the polymer components intimately.

Dry blend: The propylene-based elastomer, the second polypropylenehomopolymer, and other optional components may be dry blended and feddirectly into the fiber or nonwoven process extruders. Dry blending isaccomplished by combining the propylene-based elastomer, the secondpolypropylene homopolymer, and other optional components in a dryblending equipment. Such equipment and processes are well known in theart and include a drum tumbler, a double cone blender, and the like. Inthis case, the propylene-based elastomer, the second polypropylenehomopolymer, and other optional components are melted (where applicable)and homogenized in the process extruder similar to the melt blendprocess. Instead of making the pellets, the homogenized molten polymeris delivered to the die or spinneret to form the fiber and fabric.

Process for Producing Nonwoven Fabric of Fibers

The invention further discloses a process for producing a nonwovenfabric of bi-component fibers, the process comprising: (a) forming afirst component polymer melt comprising: a first polypropylenehomopolymer, (b) forming a second component polymer melt comprising: apropylene-based elastomer and a second polypropylene homopolymer, (c)extruding (e.g., via a melt spun process or a spunbonding process) thefirst component polymer melt and the second component polymer meltthrough a die configured for a desired bi-component fiber compositionalcross-section, and (d) cooling the bi-component fibers. In such methods,the vast majority as-produced bi-component fibers are not crimped orcurled. That is, a crimp or curled portion of the bi-component fibers isless than 5 wt % of the total weight of the bi-component fibers.

Desired bi-component fiber compositional cross-sections include, but arenot limited to, side-by-side, segmented, sheath/core, island-in-the-seastructures (“matrix fibril”), and others as is known in the art. Thefirst component described herein can compose 10 wt % to 90 wt % of thebi-component fiber, or 20 wt % to 80 wt % of the bi-component fiber, or25 wt % to 60 wt % of the bi-component fiber, or 40 wt % to 75 wt % ofthe bi-component fiber. The second component can compose the balance ofthe bi-component fiber.

The method can further include (e) thermally and/or mechanicallyactivating the bi-component fiber to cause the bi-component fiber tocrimp or curl. Activation preferably occurs after the bi-componentfibers are cooled and before thermal bonding (e.g., via calendering).For example, activation can occur immediately after the fibers are laidon a forming belt. In another example, activation can occur after thecompaction roller but before calendering.

Activation can be achieved with, for example, a hot air knife, a heatedroller (e.g., using heated oil or heating coils), mechanical crimpingrollers, fabric tensioning rollers, and the like, and any combinationthereof. Thermal activation can include heating the bi-component fibersto 50° C. or greater (e.g., 50° C. to 150° C., or 75° C. to 125° C., or90° C. to 115° C.) for 1 second or greater (e.g., 1 second to 5 minutes,or 1 second to 1 minute, or 5 seconds to 15 seconds). Mechanicalactivation can include applying a force of at least 0.01 N (e.g., 0.01 Nto 10 N, or 0.1 N to 5 N, or 0.5 N to 2 N) to the bi-component fibers.Thermal and/or mechanical activation can cause the fibers to have ashrinkage of at least 5% (e.g., 5% to 80%, or 20% to 75%, or 40% to65%), as determined in accordance with ASTM D2259-02(2016).

The spunbonding process in certain embodiments involves the process ofmelt-extruding (or “extruding”) the desired material through one or moredies, the stream of molten material then being attenuated (drawn) bypressurized air, creating a venturi effect. The material may be added totheir respective melt-extruder as pellets having desirable additives, oradditives may be combined in this step.

In particular, the formation of bi-component fibers is accomplished byextruding the molten material through an appropriate die as known in theart to produce the desired bi-component fiber compositionalcross-section, followed by quenching the molten material (having adesirable melt temperature within the die) with a quench air system thetemperature of which may be controlled. Common quench air systemsinclude those that deliver temperature controlled air in a cross-flowdirection. Filaments are then pulled away from the one or morespinnerets and thus attenuated. To accomplish this, the filaments areattenuated by passing through a venturi device in which due topressurized air flow, accelerates and/or attenuates the filaments.Increasing the air velocity within the venturi device may be done by avariety of methods described in the art, including raising the airpressure within the venturi device. Typically, increasing this airvelocity (for example by increasing air pressure) results in increasedfilament velocity and greater filament attenuation. The higher the airpressure, the more the polymer melts of the bi-component fibers areaccelerated and so attenuated, in terms of speed and denier of the fiberthat is formed therefrom. To achieve finer fibers, high air pressuresare desirable. However, this is balanced by the tendency for thefilaments to break due to excessive pressure. The polymer melts of thebi-component fibers described herein can be attenuated using higher airpressures than is typical in other spunbond processes. In anyembodiment, the attenuating air pressure used in the spunbonding processis greater than 2000 Pa or 3000 Pa or 4000 Pa or 6000 Pa, and less than600 kPa or 500 kPa or 400 kPa in other embodiments; and is within arange from 2000 Pa or 3000 Pa or 4000 Pa to 8000 Pa or 10,000 Pa or15,000 Pa in other embodiments. Such air pressure may be generated in aclosed area where the fibers are attenuated such as a “cabin,” and theair pressure therein is sometimes referred to as a “cabin pressure.”

Air attenuation can be accomplished by any means such as described andthe process is not limited to any particular method of attenuating thefilaments. In any embodiment, the venturi effect to attenuate the fibersis obtained by drawing the filaments of polymer melts of thebi-component fibers using an aspirator slot (slot draw), which runs thewidth of the machine. In another embodiment, the venturi effect isobtained by drawing the filaments through a nozzle or aspirator gun.Multiple guns can be used, since orifice size can be varied to achievethe desired effect. Bi-component fibers thus formed are collected onto ascreen (“wire”) In any embodiment, or porous forming belt in anotherembodiment to form a fabric of the filaments. Typically, a vacuum ismaintained on the underside of the belt to promote the formation of auniform fabric and to remove the air used to attenuate the filaments andcreating the air pressure. The actual method of air attenuation is notcritical, as long as the desirable accelerating air velocity, (oftenreflected by the air pressure), and hence venturi effect, is obtained toattenuate the bi-component fibers.

Pressure in the die block in any embodiment is generated by a gear pump.The method of forming the pressure in the die block is not critical, butthe pressure inside the die block ranges from 35 bar to 50 bar (3500 kPato 5000 kPa) In any embodiment, and from 36 bar to 48 bar (3600 kPa to4800 kPa) in another embodiment, and from 37 bar to 46 bar (3700 kPa to4600 kPa) in yet another embodiment.

The melt temperature in the die of the polymer melts of the bi-componentfibers ranges from 200° C. to 260° C. In any embodiment, and from 200°C. to 250° C. in yet another embodiment, and ranges from 210° C. to 245°C. in yet another embodiment.

In certain embodiments, the spunbond line throughput is within a rangefrom 150 kg/hr or 170 kg/hr to 200 kg/hr or 270 kg/hr to 300 kg/hr. Incertain other embodiments, the spunbond line throughput per hole iswithin a range from 0.20 grams/hole/minute or 0.30 grams/hole/minute or0.40 grams/hole/minute to 0.60 grams/hole/minute or 0.70grams/hole/minute or 0.90 grams/hole/minute.

In certain embodiments, the spunbond process is conducted at a spinningspeed within a range from 700 m/min or 900 m/min or 1100 m/min or 1300m/min or 1500 m/min to 2000 m/min, or 2500 m/min, or 3000 m/min, or 3500m/min, or 4000 m/min, or 4500 m/min, or 5000 m/min.

In forming propylene-based fabrics, there are any number of ways ofdispersing or distributing the bi-component fibers to form a uniformfabric. In any embodiment, a deflector is used, either stationary ormoving. In another embodiment, static electricity or air turbulence isused to improve fabric uniformity. Other means may also be used as isknown in the art. In any case, the formed fabric typically passesthrough compression rolls to improve fabric integrity. The fabric, inany embodiment, is then passed between heated calender rolls where theraised lands on one roll bond the fabric at certain points to furtherincrease the spunbonded fabric integrity. The compression and heatedcalender can be isolated from the area where the filaments are formed inany embodiment.

Preferably, the thus formed fabrics (bonded or unbonded) are exposed toa cooling environment to a temperature below 50° C., or 45° C., or 40°C., or 45° C., or 40° C., or within a range from 20° C. to 50° C.Cooling can be effected by any means such as cooling air, or chillrollers. Following the cooling, the fabrics are heated, preferably on acalender roll, heated air or heated oven environment or the like, to atemperature of at least 50° C., or 55° C., or 60° C., or 65° C., or 70°C., or 75° C., or 80° C., or 85° C., or 90° C., or within a range from50° C., or 55° C. to 80° C., or 90° C., or 100° C., or 125° C., or 155°C. More particularly, heat may be applied by any suitable method knownin the art, such as heated air, infrared heaters, heated nipped rolls,or partial wrapping of the fabric or laminate around one or more heatedrolls or steam canisters, and the like. Heat may also be applied to thegrooved rolls themselves. It should also be understood that othergrooved roll arrangement are equally suitable, such as two grooved rollspositioned immediately adjacent to one another. The percent bonded areais typically 18% to 25% of the fabric. It is possible, and preferable todecrease the bonding area, for example, to 10% to 15% of the fabric toenhance the loftiness of the fabrics and preserve the curling of fibers.

Various additional potential processing and/or finishing steps known inthe art, such as slitting, treating, printing graphics, and the like,may be performed without departing from the spirit and scope of theinvention. For instance, the fabric or laminate comprising the fabricmay optionally be mechanically stretched in the cross-machine and/ormachine directions to enhance extensibility. In any embodiment, thefabric or laminate may be coursed through two or more rolls that havegrooves in the CD and/or MD directions. Such grooved satellite/anvilroll arrangements are described in US 2004/0110442 and US 2006/0151914and U.S. Pat. No. 5,914,084. For instance, the fabric or laminate may becoursed through two or more rolls that have grooves in the CD and/or MDdirections. The grooved rolls may be constructed of steel or other hardmaterial (such as a hard rubber). Besides grooved rolls, othertechniques may also be used to mechanically stretch the composite in oneor more directions. For example, the composite may be passed through atenter frame that stretches the composite. Such tenter frames are wellknown in the art and described, for instance, in US 2004/0121687.

No matter how formed and oriented, the propylene-based fabrics comprisefibers having an average diameter of less than 20 or 17 or 15 or 12 μmin certain embodiments, alternatively from 0.5, or 1, or 2, or 3, or 4to 12, or 15, or 17, or 20 μm, and/or a denier (g/9000 m) of less than2.0 or 1.9 or 1.8 or 1.6 or 1.4 or 1.2 or 1.0 in certain embodiments,alternatively from 0.2, or 0.4 or 0.6 to 1.0, or 1.2 or 1.4 or 1.6 or1.8, or 2.0. Such fabrics, when oriented at a temperature (calender settemperature) within a range from 110 to 150° C. have a MD TensileStrength (WSP 110.4 (05)) of greater than 20 or 25 N/5 cm in certainembodiments. The fabrics have a CD Tensile Strength (WSP 110.4 (05)) ofgreater than 10 N/5 cm or 15 N/5 cm when oriented at a temperature(calender set temperature) within a range from 110° C. to 150° C. inother embodiments.

In certain embodiments, the one or more propylene-based fabrics may forma laminate either with itself or with other secondary layers. Thelamination of the various layers can be done such that CD and/or MDorientation is imparted into the fabric or laminate, especially in thecase where the laminate includes at least one elastomeric layer. Manyapproaches may be taken to form a laminate comprising an elastomericfilm and/or fabric layer which remains elastomeric once the laminatelayers are bonded together. One approach is to fold, corrugate, crepe,or otherwise gather the fabric layer prior to bonding it to theelastomeric film. The gathered fabric is bonded to the film at specifiedpoints or lines, not continually across the surface of the film. Whilethe film/fabric is in a relaxed state, the fabric remains corrugated orpuckered on the film; once the elastomeric film is stretched, the fabriclayer flattens out until the puckered material is essentially flat, atwhich point the elastomer stretching ceases.

Another approach is to stretch the elastomeric film/fabric, then bondthe fabric to the film while the film is stretched. Again, the fabric isbonded to the film at specified points or lines rather than continuallyacross the surface of the film. When the stretched film is allowed torelax, the fabric corrugates or puckers over the unstretched elastomericfilm.

Another approach is to “neck” the fabric prior to bonding it to theelastomer layer as described in U.S. Pat. Nos. 5,336,545, 5,226,992,4,981,747, and/or 4,965,122. Necking is a process by which the fabric ispulled in one direction, which causes the fibers in the fabric to slidecloser together, and the width of the fabric in the directionperpendicular to the pulling direction is reduced. If the necked fabricis point-bonded to an elastomeric layer, the resulting laminate willstretch somewhat in a direction perpendicular to the direction in whichthe fabric was pulled during the necking process, because the fibers ofthe necked fabric can slide away from one another as the laminatestretches.

Laminates

This invention further provides a laminate comprising one or more layersof a nonwoven fabric comprising bi-component fibers described herein.

Preferably, the laminates are allowed to cool, if previously heated, toa temperature below 50° C., or 45° C., or 40° C., or 45° C., or 40° C.,or within a range from 20° C. to 50° C. Cooling can be effectuated byany means such as cooling air, or chill rollers. Following the cooling,the fabrics are activated such as by heating the laminates in a similarfashion to activation of the individual fabrics described above. Inparticular the laminates may be heated, preferably on a calender roll,heated air or heated oven environment or the like, to a temperature ofat least 50° C., or 55° C., or 60° C., or 65° C., or 70° C., or 75° C.,or 80° C., or 85° C., or 90° C., or within a range from 50° C., or 55°C. to 80° C., or 90° C., or 100° C., or 120° C. More particularly, heatmay be applied by any suitable method known in the art, such as heatedair, infrared heaters, heated nipped rolls, or partial wrapping of thefabric or laminate around one or more heated rolls or steam canisters,and the like. Heat may also be applied to the grooved rolls themselves.It should also be understood that other grooved roll arrangement areequally suitable, such as two grooved rolls positioned immediatelyadjacent to one another.

Yet another approach is to activate the laminate by a physicaltreatment, modification or deformation of the laminate, said activationbeing performed by mechanical means. For example, the laminate may beincrementally stretched by using intermeshing rollers, as discussed inU.S. Pat. No. 5,422,172, or US 2007/0197117 to render the laminatestretchable and recoverable. Finally, the film or fabric may be suchthat it needs no activation and is simply formed onto and/or bound to asecondary layer to form a laminate.

In some embodiments, the laminates comprising one or more secondarylayers comprising other fabrics, nets, coform fabrics, scrims, and/orfilms prepared from natural and/or synthetic materials. The materialsmay be extensible, elastic or plastic in certain embodiments. Inparticular embodiments, the one or more secondary layers comprisematerials selected from the group consisting of polypropylene,polyethylene, plastomers, polyurethane, polyesters such as polyethyleneterephthanlate, polylactic acid, polyvinyl chloride,polytetrafluoroethylene, styrenic block copolymers, ethylene vinylacetate copolymers, poly amide, polycarbonate, cellulosics (e.g.,cotton, Rayon™, Lyocell™ Tencil™), wood, viscose, and blends of any twoor more of these materials. Any secondary layer may also comprise (orconsist essentially of) any material that is elastic, examples of whichinclude propylene-α-olefin elastomer, natural rubber (NR), syntheticpolyisoprene (IR), butyl rubber (copolymer of isobutylene and isoprene,IIR), halogenated butyl rubbers (chloro-butyl rubber: CIIR; bromo-butylrubber: BUR), polybutadiene (BR), styrene-butadiene rubber (SBR),nitrile rubber, hydrogenated nitrile rubbers, chloroprene rubber (CR),poly chloroprene, neoprene, EPM (ethylene-propylene rubber) and EPDMrubbers (ethylene-propylene-diene rubber), epichlorohydrin rubber (ECO),polyacrylic rubber (ACM, ABR), silicone rubber, fluorosilicone rubber,fiuoroelastomers, perfiuoroelastomers, polyether block amides (PEBA),chlorosulfonated polyethylene (CSM), ethylene-vinyl acetate (EVA),thermoplastic elastomers (TPE), thermoplastic vulcanizates (TPV),thermoplastic polyurethane (TPU), thermoplastic olefins (TPO),polysulfide rubber, or blends of any two or more of these elastomers. Incertain embodiments, the one or more elastic layers comprisepropylene-a-olefin elastomer, styrene-butadiene rubber, or blendsthereof. In yet other embodiments, the one or more elastic layersconsist essentially of propylene-a-olefin elastomer(s). In a particularembodiment, styrenic-based elastomers (polymers comprising at least 10wt % styrene or substituted-styrene-derived units) are absent from themultilayer fabric.

The secondary layer(s) may be in the form of films, fabrics, or both.Films may be cast, blown, or made by any other suitable means. When thesecondary layers are fabrics, the secondary layers can be meltspun,dry-laid or wet-laid fabrics. The dry-laid processes include mechanicalmeans, such as how carded fabrics are produced, and aerodynamic means,such as, air-laid methods. Dry-laid nonwovens are made with staple fiberprocessing machinery such as cards and garnetts, which are designed tomanipulate staple fibers in the dry state. Also included in thiscategory are nonwovens made from fibers in the form of tow, and fabricscomposed of staple fibers and stitching filaments or yarns, namely,stitchbonded nonwovens. Fabrics made by wet-laid processes made withmachinery associated with pulp fiberizing, such as hammer mills, andpaperforming. Web-bonding processes can be described as being chemicalprocesses or physical processes. In any case, dry- and wet-laid fabricscan be jet and/or hydroentangled to form a spunlace fabric as is knownin the art. Chemical bonding refers to the use of water-based andsolvent-based polymers to bind together the fibrous webs. These binderscan be applied by saturation (impregnation), spraying, printing, orapplication as a foam. Physical bonding processes include thermalprocesses such as calendering and hot air bonding, and mechanicalprocesses such as needling and hydroentangling. Spunlaid nonwovens aremade in one continuous process: fibers are spun by melt extrusion andthen directly dispersed into a web by deflectors or can be directed withair streams.

In certain embodiments, the propylene-based elastomer may be formed intocoform fabrics. Methods for forming such fabrics are described in, forexample, U.S. Pat. Nos. 4,818,464 and 5,720,832. Generally, fabrics oftwo or more different thermoplastic and/or elastomeric materials may beformed.

The nonwoven fabric of fibers can be used to make articles, such aspersonal care products, baby diapers, training pants, absorbentunderpads, swim wear, wipes, feminine hygiene products, bandages, woundcare products, medical garments, surgical gowns, filters, adultincontinence products, surgical drapes, coverings, garments, cleaningarticles and apparatus.

Example Embodiments

A first embodiment is a method comprising: (a) extruding a bi-componentfiber comprising: a first component comprising a first polypropylenehomopolymer; and a second component comprising a blend that comprises apropylene-based elastomer and a second polypropylene homopolymer,wherein the blend has a melt flow rate that is at least 20% greater thanor at least 20% less than a melt flow rate of the first polypropylenehomopolymer; (b) cooling the bi-component fiber; and (c) thermallyand/or mechanically activating the bi-component fiber to cause thebi-component fiber to curl. This embodiment may optionally include oneor more of the following: Element 1: wherein a weight ratio of thepropylene-based elastomer and the second polypropylene homopolymer inthe blend is 10:90 to 90:10; Element 2: wherein a weight ratio of thepropylene-based elastomer and the second polypropylene homopolymer inthe blend is 40:60 to 90:10; Element 3: wherein a weight ratio of thepropylene-based elastomer and the second polypropylene homopolymer inthe blend is 10:90 to 60:40; Element 4: wherein the bi-component fiberis thermally activated by exposing the bi-component fiber to 50° C. to150° C. for 1 second to 5 minutes; Element 5: wherein the bi-componentfiber is thermally activated by exposing the bi-component fiber to 90°C. to 115° C. for 5 seconds to 15 seconds; Element 6: wherein thebi-component fiber is mechanically activated by exposing thebi-component fiber to a force of 0.01 N to 10 N; Element 7: wherein thebi-component fiber is mechanically activated by exposing thebi-component fiber to a force of 0.1 N to 5 N; Element 8: wherein thebi-component fiber after cooling is substantially straight and afteractivating has a shrinkage of a least 25%; Element 9: wherein thebi-component fiber after cooling is substantially straight and afteractivating has a shrinkage of a least 45%; Element 10: wherein a weightratio of the first component and the second component in thebi-component fiber is 10:90 to 90:10; Element 11: wherein a weight ratioof the first component and the second component in the bi-componentfiber is 40:60 to 80:20; Element 12: wherein a compositionalcross-section is side-by-side, segmented, sheath/core, orisland-in-the-sea; Element 13: the method further comprising: producinga nonwoven article with the bi-component fiber; and Element 14: themethod further comprising: producing a laminated article with thebi-component fiber. Example combinations include, but are not limitedto, one of Elements 1-3 in combination with one or more of Elements 4-7;one of Elements 1-3 in combination with one of Elements 8-9; one ofElements 1-3 in combination with one of Elements 10-11; one of Elements1-3 in combination with one or more of Elements 12-14; one of Elements10-11 in combination with one or more of Elements 4-7; one of Elements10-11 in combination with one of Elements 8-9; one of Elements 10-11 incombination with one or more of Elements 12-14; one or more of Elements4-7 in combination with one of Elements 8-9; one or more of Elements 4-7in combination with one or more of Elements 12-14; and any combinationof these combinations.

By “substantially straight” what is meant is that the fiber strandthroughout its length has an overall bend from 180° of no more than ±10°or ±5°. For instance, there may be one, two or more bends or kinks in astrand, but overall the strand is substantially straight as definedhere.

A second embodiment is a bi-component fiber comprising: a firstcomponent comprising a first polypropylene homopolymer; and a secondcomponent comprising a blend that comprises a propylene-based elastomerand a second polypropylene homopolymer, wherein the blend has a meltflow rate that is at least 20% greater than or at least 20% less than amelt flow rate of the first polypropylene homopolymer. This embodimentmay optionally include one or more of the following: Element 1; Element2; Element 3; Element 10; Element 11; and Element 12. Examplecombinations include, but are not limited to, one of Elements 1-3 incombination with one of Elements 10-11 and optionally in furthercombination with Element 12; one of Elements 1-3 in combination withElement 12; and one of Elements 10-11 in combination with Element 12.

A third embodiment is a nonwoven article comprising the bi-componentfiber of the second embodiment, optionally including one or more ofElements 1-3 and 10-12.

A fourth embodiment is a laminated article comprising the bi-componentfiber of the second embodiment, optionally including one or more ofElements 1-3 and 10-12.

One or more illustrative embodiments incorporating the inventionembodiments disclosed herein are presented herein. Not all features of aphysical implementation are described or shown in this application forthe sake of clarity. It is understood that in the development of aphysical embodiment incorporating the embodiments of the presentinvention, numerous implementation-specific decisions must be made toachieve the developer's goals, such as compliance with system-related,business-related, government-related and other constraints, which varyby implementation and from time to time. While a developer's effortsmight be time-consuming, such efforts would be, nevertheless, a routineundertaking for those of ordinary skill in the art and having benefit ofthis disclosure.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsand steps.

To facilitate a better understanding of the embodiments of the presentinvention, the following examples of preferred or representativeembodiments are described. In no way should the following examples beread to limit, or to define, the scope of the invention.

Examples

Example 1. Bi-component fibers were produced with a side-by-side and asheath/core compositional cross-section where the first component was apolypropylene homopolymer having an MFR (ASTM D1238-13, 2.16 kg, 230°C.) of 36 g/10 min and the second component was a 50:50 blend of thesame polypropylene homopolymer and a polypropylene-polyethylenecopolymer having an MFR (ASTM D1238-13, 2.16 kg, 230° C.) of 48 g/10 min(Sheath/Core Bi-Component Fiber and Side-by-Side Bi-Component Fiber).The blend had an MFR (ASTM D1238-13, 2.16 kg, 230° C.) of 45 g/10 min.

Control fibers were produced that consisted of the polypropylenehomopolymer having an MFR (ASTM D1238-13, 2.16 kg, 230° C.) of 36 g/10min (Single Component Fiber).

The weight ratio of the first component to the second component werevaried from 20:80 to 80:20. After cooling the as-produced fibers, thebi-component and control fibers were thermally activated by exposure to100° C. for 15 seconds, which resulted in curling of the filaments. Theshrinkage (ASTM D2259-02(2016)) is reported in FIG. 1.

The control filaments have less than 7% shrinkage. Whereas, thebi-component fibers can have almost 80% shrinkage. As the weight ratioof the first component to the second component increases, so does theamount of shrinkage.

Example 2. FIG. 2A is a scanning electron micrograph of bi-componentfibers having 40 wt % ExxonMobil™ PP3155E5 and 60 wt % of a 30:70 blendof ExxonMobil™ PP3155E5+Vistamaxx™7050 as-produced before mechanicalactivation, and FIG. 2B is that sample after mechanical activation bymanually applying force with a brush. This illustrates the straightfibers as-produced and curled fibers after activation.

Example 3. Bi-component fibers were produced with a side-by-sidecompositional cross-section where the first component was apolypropylene homopolymer having an MFR (ASTM D1238-13, 2.16 kg, 230°C.) of 36 g/10 min and the second component was a 60:40 blend of thesame polypropylene homopolymer and a polypropylene-polyethylenecopolymer having an MFR (ASTM D1238-13, 2.16 kg, 230° C.) of 48 g/10min.

FIGS. 3A and 3B is a light micrographs of the fibers as-produced beforethermal activation, and FIGS. 3C and 3D is that sample after thermalactivation at 100° C. for 15 seconds. This illustrates the straightfibers as-produced and curled fibers after activation.

Example 4. Bi-component fibers were produced with a side-by-sidecompositional cross-section or a sheath/core compositional cross-sectionaccording to the compositions in Table 1. Control fibers were producedthat consisted of the polypropylene homopolymer having an MFR (ASTMD1238-13, 2.16 kg, 230° C.) of 36 g/10 min.

TABLE 1 Comp. 1 to Component 2 Comp. 2 Wt. Blend Ratio Sample Component1 Component 2 Ratio (Blend MFR) 1A ExxonMobil ™ ExxonMobil ™ 50/50 30/70PP3155E5 PP3155E5 + (~45 g/10 min) Vistamaxx ™ 7050 1B ExxonMobil ™ExxonMobil ™ 40/60 30/70 PP3155E5 PP3155E5 + (~45 g/10 min)Vistamaxx ™ 7050 1C ExxonMobil ™ ExxonMobil ™ 30/70 30/70 PP3155E5PP3155E5 + (~45 g/10 min) Vistamaxx ™ 7050 1D ExxonMobil ™ ExxonMobil ™20/80 30/70 PP3155E5 PP3155E5 + (~45 g/10 min) Vistamaxx ™ 7050 2AExxonMobil ™ ExxonMobil ™ 50/50 60/40 PP3155E5 PP3155E5 + (~28 g/10 min)Vistamaxx ™ 7020 2B ExxonMobil ™ ExxonMobil ™ 40/60 60/40 PP3155E5PP3155E5 + (~28 g/10 min) Vistamaxx ™ 7020 2C ExxonMobil ™ ExxonMobil ™30/70 60/40 PP3155E5 PP3155E5 + (~28 g/10 min) Vistamaxx ™ 7020 2DExxonMobil ™ ExxonMobil ™ 20/80 60/40 PP3155E5 PP3155E5 + (~28 g/10 min)Vistamaxx ™ 7020 3A ExxonMobil ™ ExxonMobil ™ 50/50 95/5 PP3155E5PP3155E5 + (~48 g/10 min) Vistamaxx ™ 8880 3B ExxonMobil ™ ExxonMobil ™40/60 95/5 PP3155E5 PP3155E5 + (~48 g/10 min) Vistamaxx ™ 8880 3CExxonMobil ™ ExxonMobil ™ 30/70 95/5 PP3155E5 PP3155E5 + (~48 g/10 min)Vistamaxx ™ 8880 3D ExxonMobil ™ ExxonMobil ™ 20/80 95/5 PP3155E5PP3155E5 + (~48 g/10 min) Vistamaxx ™ 8880

Example 5. Three sets of fibers were produced. First, a control set offibers were produced in a side-by-side confirmation of ExxonMobil™PP3155 and another polypropylene homopolymer (PP/PP Bi-Component Fiber).Second, a bi-component fiber of the invention was produced with Achieve™Advanced PP3854 as the first component and ExxonMobil™ PP3155E5 as thesecond component in a side-by-side configuration (PP/Achieve BlendBi-Component Fiber). Third, a blend of ExxonMobil™ PP3155 andVistamaxx™7020 was produced as a monocomponent fiber (PP Blend SingleComponent Fiber). Each set of fibers was produced with different weightratios of each component. The fibers were thermally activated byexposure to 100° C. for 15 seconds and the shrinkage was measured (seeFIG. 4). The bi-component fiber of the invention is the only sample withappreciable shrinkage including up to 55% with 70 wt % of the firstcomponent and 30 wt % of the second component.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein.

While compositions and methods are described in terms of “comprising,”“containing,” or “including” various components or steps, thecompositions and methods can also “consist essentially of” or “consistof” the various components and steps.

1. A method comprising: extruding a bi-component fiber comprising: afirst component comprising a first polypropylene homopolymer; and asecond component comprising a blend that comprises a propylene-basedelastomer and a second polypropylene homopolymer, wherein the blend hasa melt flow rate that is at least 20% greater than or at least 20% lessthan a melt flow rate of the first polypropylene homopolymer; coolingthe bi-component fiber; and activating the bi-component fiber to causethe bi-component fiber to curl wherein the step of activating isperformed thermally, mechanically, or through a combination of thermaland mechanical action.
 2. The method of claim 1, wherein a weight ratioof the propylene-based elastomer and the second polypropylenehomopolymer in the blend is 10:90 to 90:10.
 3. The method of claim 1,wherein a weight ratio of the propylene-based elastomer and the secondpolypropylene homopolymer in the blend is 40:60 to 90:10.
 4. The methodof claim 1, wherein the bi-component fiber is thermally activated byexposing the bi-component fiber to 50° C. to 150° C. for 1 second to 5minutes.
 5. The method of claim 1, wherein the bi-component fiber isthermally activated by exposing the bi-component fiber to 90° C. to 115°C. for 5 seconds to 15 seconds.
 6. The method of claim 1, wherein thebi-component fiber is mechanically activated by exposing thebi-component fiber to a force of 0.01 N to 10 N.
 7. The method of claim1, wherein the bi-component fiber is mechanically activated by exposingthe bi-component fiber to a force of 0.1 N to 5 N.
 8. The method ofclaim 1, wherein the bi-component fiber after cooling is substantiallystraight and after activating has a shrinkage of a least 25%.
 9. Themethod of claim 1, wherein the bi-component fiber after cooling issubstantially straight and after activating has a shrinkage of a least45%.
 10. The method of claim 1, wherein a weight ratio of the firstcomponent and the second component in the bi-component fiber is 10:90 to90:10.
 11. The method of claim 1, wherein a weight ratio of the firstcomponent and the second component in the bi-component fiber is 40:60 to80:20.
 12. The method of claim 1, wherein a compositional cross-sectionis side-by-side, segmented, sheath/core, or island-in-the-sea.
 13. Themethod of claim 1 further comprising producing a nonwoven article withthe bi-component fiber.
 14. The method of claim 1 further comprisingproducing a laminated article with the bi-component fiber.
 15. Abi-component fiber comprising: a first component comprising a firstpolypropylene homopolymer; and a second component comprising a blendthat comprises a propylene-based elastomer and a second polypropylenehomopolymer, wherein the blend has a melt flow rate that is at least 20%greater than or at least 20% less than a melt flow rate of the firstpolypropylene homopolymer.
 16. The bi-component fiber of claim 15,wherein a weight ratio of the propylene-based elastomer and the secondpolypropylene homopolymer in the blend is 10:90 to 90:10.
 17. Thebi-component fiber of claim 15, wherein a weight ratio of the firstcomponent and the second component in the bi-component fiber is 10:90 to90:10.
 18. The bi-component fiber of claim 15, wherein a compositionalcross-section is side-by-side, segmented, sheath/core, orisland-in-the-sea.
 19. A nonwoven article comprising the bi-componentfiber of claim
 15. 20. A laminated article comprising the bi-componentfiber of claim 15.